The Cubomedusæ

Part Ii: General Description of the Anatomy of the Cubomedusæ 7

A. CHARYBDEA XAYMACANA 7

a. Environment and Habit of Life 7

b. External Anatomy 8

2. Form of Bell 8

3. Pedalia 8

4. Sensory Clubs 9

5. The Bell Cavity and its Structures 10

(a) Proboscis 11

(b) Suspensoria, or Mesogonia 11

(c) Interradial funnels, or funnel cavities 11

(d) Velarium 12

(e) Frenula 12

(f) Musculature 12

(g) Nerve ring 13

c. Internal Anatomy 13

6. Stomach 13

7. Phacelli 14

8. Peripheral Part of the Gastro-Vascular System 14

(a) Stomach Pockets (Valves and Mesogonial Pockets) 14

(b) Marginal Pockets 17

(c) Canals of the Sensory Clubs and Tentacles 17

9. Reproductive Organs 19

10. Floating and Wandering Cells 20

B. TRIPEDALIA CYSTOPHORA 22

a. Habitat 22

b. External Anatomy 23

c. Internal Anatomy 24

Part Iii: Description of Special Parts of the Anatomy 27

A. VASCULAR LAMELLÆ 27

B. NERVOUS SYSTEM 37

LITERATURE 57

TABLE OF REFERENCE LETTERS 58

DESCRIPTION OF FIGURES 60

INTRODUCTION.

Jelly-fish offer to the lover of natural history an inexhaustible store of beauty and attractiveness. One who has studied them finds within him a ready echo to Haeckel’s statement that when first he visited the seacoast and was introduced to the enchanted world of marine life, none of the forms that he then saw alive for the first time exercised so powerful an attraction upon him as the Medusæ. The writer counts it a rare stroke of fortune that he was led to the study of a portion of the group by the discovery of two new species of Cubomedusæ in Kingston Harbor, Jamaica, W. I., while he was with the Johns Hopkins Marine Laboratory in June of 1896.

The Cubomedusæ are of more than passing interest among jelly-fish, both because of their comparative rarity and because of the high degree of development attained by their nervous system. One fact alone suffices to attract at once the attention of the student of comparative morphology--that here among the lowly-organized Cœlenterates we find an animal with eyes composed of a cellular lens contained in a pigmented retinal cup, in its essentials analogous to the vertebrate structure. Perhaps this and other facts about the Cubomedusæ would be more generally known, had they not been to a certain extent hidden away in Claus’s paper on Charybdea marsupialis (’78), which, while a record of careful and accurate work, is in many respects written and illustrated so obscurely that it is very doubtful whether one could arrive at a clear understanding of its meaning who was not pretty well acquainted with Charybdea beforehand.

Before Claus’s paper was received at this laboratory, H. V. Wilson went over essentially the same ground upon a species of Chiropsalmus taken at Beaufort, N. C. When the article on Charybdea marsupialis appeared, however, the results were so similar that Wilson did not complete for publication the careful notes and drawings he had made.

Haeckel’s treatment of the Cubomedusæ in his “System” (’79) in the Challenger Report (’81) is much more lucid than Claus’s; but the extended scope of his work and the imperfect preservation of his material prevented a detailed investigation, and for a more complete and readily intelligible account of the structure of the Cubomedusæ a larger number of figures is desirable.

In the foregoing facts lies whatever excuse is necessary for repeating in the present paper much that has already seen print in one form or another.

Part I: Systematic.

It seems advisable first of all to establish the systematic position of the two newly found species, Charybdea Xaymacana and Tripedalia cystophora. Haeckel’s classification, as given in his “System der Medusen,” is an excellent one and will be followed in this case. One of the new species, however, will not classify under either of Haeckel’s two families, so that for it a new family has been formed and named the Tripedalidæ. In showing the systematic position of the two new forms, an outline of Haeckel’s classification will be given, so far as it concerns our species, together with the additions that have been made necessary.

CUBOMEDUSÆ (Haeckel, 1877).

Characteristics: Acraspeda with four perradial sensory clubs which contain an auditory club with endodermal otolith sac and one or several eyes. Four interradial tentacles or groups of tentacles. Stomach with four wide perradial rectangular pockets, which are separated by four long and narrow interradial septa, or cathammal plates. Gonads in four pairs, leaf-shaped, attached along one edge to the four interradial septa. They belong to the subumbrella, and are developed from the endoderm of the stomach pockets, so that they project freely into the spaces of the pockets.

Family I: CHARYBDEA (Gegenbaur, 1856).

Cubomedusæ with four simple interradial tentacles; without marginal lobes in the velarium, but with eight marginal pockets; without pocket arms in the four stomach pockets.

Genus: Charybdea.

Charybdeidæ with four simple interradial tentacles with pedalia; with velarium suspended, with velar canals and four perradial frenula. Stomach flat and low, without broad suspensoria. Four horizontal groups of gastric filaments, simple or double, tuft or brush-shaped, limited to the interradial corners of the stomach.

Species: Charybdea Xaymacana (Fig. 1).

Bell a four-sided pyramid with the corners more rounded than angular, yet not so rounded as to make the umbrella bell-shaped. The sides of the pyramid parallel in the lower two-thirds of the bell, in the upper third curving inward to form the truncation; near the top a slight horizontal constriction. Stomach flat and shallow. Proboscis with four oral lobes, hanging down in bell cavity a distance of between one-third and one-half the height of bell; very sensitive and contractile, so that it can be inverted into the stomach. The four phacelli epaulette-shaped, springing from a single stalk. Distance of the sensory clubs from the bell margin one-seventh or one-eighth the height of bell. Velarium in breadth about one-seventh the diameter of the bell at its margin. Four velar canals in each quadrant; each canal forked at the ends, at times with more than two branches. Pedalia flat, scalpel-shaped, between one-third and one-half as long as the height of bell. The four tentacles, when extended, at least eight times longer than the bell. Sexes separate. Height of bell, 18-23 mm.; breadth, about 15 mm. (individuals with mature reproductive elements); without pigment. Found at Port Henderson, Kingston Harbor, Jamaica.

As may be seen from the above, C. Xaymacana differs only a little from the C. marsupialis of the Mediterranean. Claus mentions in the latter a more or less well defined asymmetry of the bell, which he connects with a supposed occasional attachment by the proboscis to algæ. In C. Xaymacana I never noticed but that the bell was perfectly symmetrical. C. Xaymacana is about two-thirds the size given by Claus for his examples of C. marsupialis, which were not then sexually mature. It has 16 velar canals instead of 24 (32), as given by Haeckel, or 24 as figured by Claus. Difference in size and in number of velar canals are essentially the characteristics upon which Haeckel founded his Challenger species, C. Murrayana.

Family II: CHIRODROPIDÆ (Haeckel, 1877).

Cubomedusæ with four interradial groups of tentacles; with sixteen marginal pockets in the marginal lobes of the velarium, and with eight pocket arms, belonging to the exumbrella, in the four stomach pockets.

This family is represented in American waters by a species of Chiropsalmus, identified by H. V. Wilson as C. quadrumanus, found at Beaufort, North Carolina.

Family III: TRIPEDALIDÆ (1897).

Cubomedusæ with four interradial groups of tentacles, each group having three tentacles carried by three distinct pedalia; without marginal lobes in the velarium; with sixteen marginal pockets; without pocket arms in the stomach pockets.

Genus: Tripedalia.

For the present the characteristics of family and genus must necessarily be for the most part the same. The genus is distinguished by having twelve tentacles in four interradial groups of three each; velarium suspended by four perradial frenula; canals in the velarium; stomach projecting somewhat convexly into the bell cavity, with relatively well-developed suspensoria; four horizontal groups of gastric filaments, each group brush-shaped, limited to the interradial corners of the stomach.

Species: Tripedalia cystophora (Fig. 17).

Shape of bell almost exactly that of a cube with rounded edges; the roof but little arched. The horizontal constriction commonly seen near the top of the bell in the Cubomedusæ not present. Proboscis with four oral lobes; hanging down in the bell cavity generally more than half the depth of the cavity and at times even to the bell margin. In the gelatine of the proboscis an irregular number (15-21) of sensory organs resembling otocysts, from the presence of which comes the specific name. Phacelli brush-shaped, composed of from seven to thirteen filaments springing from a single stalk in each quadrant, or rarely from two separate stalks in one of the quadrants. Distance of the sensory clubs from the bell margin about one-fifth or one-fourth of the height of bell. Breadth of velarium about one-sixth the diameter of bell at margin; with six velar canals in each quadrant; the canals simple, unforked. Pedalia flattened, shaped like a slender knife blade, about half as long as the height of the bell. Tentacles at greatest extension observed two and a half times the length of pedalia. Sexes separate. Height of bell in largest specimens (reproductive elements mature) eight or nine mm. Breadth same as height or even greater. Color a light yellowish brown, due in large part to eggs or embryos in the stomach pockets. The reproductive organs especially prominent by reason of their similar color. Found in Kingston Harbor, Jamaica.

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